The present invention generally relates to golf clubs and, more particularly to cavity back irons filled with vibration dampening material.
The individual golf club heads in a set typically increase progressively in strike face surface area and weight as the clubs progress from the long irons to the short irons. Therefore, the club heads of the long irons have a smaller strike face surface area than the short irons and are typically more difficult for the average golfer to hit consistently well. For conventional club heads, this arises at least in part due to the smaller sweet spot of the corresponding smaller strike face.
To help the average golfer consistently hit the sweet spot of a club head, many golf clubs are available having heads with so-called cavity back designs with increased perimeter weighting. Another more recent trend has been to simply increase the overall size of the club heads, especially in the long irons. Each of these features will increase the size of the sweet spot and therefore make it more likely that a shot hit slightly off the center of gravity of the club head still makes contact with the sweet spot and flies farther and straighter as a result. One challenge for the golf club designer when maximizing the size of the club head concerns maintaining a desirable and effective overall weight of the golf club. For example, if the club head of a three iron is increased in size and weight, the club may become difficult for the average golfer to properly swing.
Another problem area for the average golfer is that of excess vibration resulting from an off center impact with the golf ball. Various types of vibration dampening have been incorporated into club heads to absorb these impact vibrations. However, there is still a need for improvement in the areas of weight redistribution, vibration dampening in golf club heads, and especially improving the sound and feel upon striking the golf ball. A significant need is to provide a golf club head that is more tolerant to a golfer""s inadvertent misplacement of the front hitting surface upon contact with the ball. In addition to inaccuracy of the shot, vibrations are indicative of a less than ideal transfer of energy from the club to the ball, and consequently represent inefficiency in the club head.
A number of golf club manufacturers have developed golf clubs that attempt to reduce the transmission of vibration up the shaft of the golf club. A manufacturer of golf club shafts called TRU-TEMPER, for example, has placed a polymer or sponge-like material in the shaft. This particular product, known as SENSICORE(trademark), is helpful, but suffers from the fact that it merely attempts to dampen vibration that has already been transmitted to the shaft.
There remains a significant need, therefore, for a golf club head that is more accurate and more forgiving and which more efficiently dampens the transmission of shock vibrations from the golf club head to the shaft.
Conceptually, the invention includes a recess in the cavity portion of a golf iron club head that is filled with a polymer material. This design accomplishes several things. First, it allows the head to have a larger volume for a given amount of weight, in that the polymer adds very little weight to the iron club head relative to the volume added. Secondly, it provides a unique way of attaching a medallion to a club head. And thirdly, it creates a spring/mass method for dampening undesirable vibrations, where the polymer is the spring and the medallion the mass.
The recess for the insertion of the polymer is preferably formed in the main body structure of the golf club head during the casting or forging process, but may also be formed subsequently by machining. Because the polymer that fills the recess is less dense than the metal material that would have filled the recess, the mass moment of inertia of the golf club is actually increased.
Additionally, ideally the polymer material is an epoxy, polyurethane or similar formable polymer that exhibits positive adherence characteristics to the main body structure of the club head. In the current preferred embodiment, once the main body structure of the golf club head has been formed, such as by investment casting, the polymer is preferably pre-formed and adhesively attached to the recess. While the actual type and make up of the material used for the recess filler is not critical, it must exhibit the properties of resiliency and elasticity. Consequently, other types of materials could be substituted for the polymer.